A heat pipe is a hermetically sealed, evacuated tube comprising a working fluid in both the liquid and vapour phase. When one end of the tube is heated the liquid turns to vapour upon absorbing the latent heat of vaporization. The hot vapour subsequently passes to the cooler end of the tube where it condenses and releases the latent heat to the tube. The condensed liquid then flows back to the hot end of the tube and the vaporization-condensation cycle repeats. Since the latent heat of vaporization is usually very large, considerable quantities of heat can be transferred along the tube and a substantially uniform temperature distribution can be achieved along the heat pipe.
Referring to FIG. 8, there is illustrated a known heat pipe heat exchanging arrangement 10 for exchanging heat, and more particularly absorbing heat from a planar surface (not shown). The exchanger 10 comprises a plurality of heat pipes 11 which are coupled along a proximal portion 11a thereof to a rear face of a panel 12. The heat pipes 11 are arranged in a substantially parallel configuration and extend along the length of the panel 12. The panel 12 is arranged to absorb heat from the planar surface (not shown) and the heat absorbed is communicated to the proximal portion 11a of the heat pipes 11 which causes the fluid (not shown) disposed therein to turn to a vapour.
The distal portion 11b of the pipes 11 are arranged to extend within a flow duct 13 along which a cooling fluid (not shown) is arranged to pass, so that the vapour which passes to the distal portion 11b of the pipes 11 can condense. The condensate, namely the cooled working fluid, can subsequently return to the proximal portion 11a of the heat pipes 11 for further absorption of heat from the panel 12. In this respect, the cooling fluid (not shown) can be arranged to extract the heat absorbed by the working fluid so that the heat pipes 11, and in particular, the fluid disposed within the heat pipes 11 can continue to absorb heat. A problem with this arrangement however, is that the temperature of the working fluid within the heat pipes 11 rises during use, which reduces the ability of the fluid to absorb further heat from the panel 12. Furthermore, it is often difficult to separately seal the distal portion 11b of each heat pipe 11 to the flow duct 13, with the result that the cooling fluid can leak out of the duct.
WO 2013/104884 discloses a heat exchanger for exchanging heat with a medium across a substantially planar surface. This is shown in FIG. 9. The exchanger 900 comprises: a heat exchanging panel 901; a fluid circuit comprising a first chamber 904 disposed at a first end of the panel 901, a second chamber 905 disposed at a second end of the panel 101, a plurality of passages 903 which extend along the panel between the first and second chambers 904, 905, and a duct 907 which extends between the first and second chamber 904, 905; a fluid disposed within the circuit; wherein, the plurality of passages 903 are arranged in thermal communication with the panel 901 and are arranged to communicate the fluid from the first chamber 904 to the second chamber 905, and the duct 907 is arranged to communicate fluid from the second chamber 905 to the first chamber 904.